Dan Brown has made a pretty decent career along the lines of "find a book with missing ancient wisdom, mayhem ensues, starring tom hanks" (with 1 paragraph cliff-hanger chapters). The theme of 'someone smart wrote it down and then we forgot it' gives value to those ancient books.
Imagine my surprise when I'm perusing reddit yesterday and find this thread "Ancient Unix books spotted at thrift store". And then to discover these were books that I had purchased new.
You see, many years ago, there was a shop in uptown waterloo "the computer book store". It later became a jewelry shop (Hatashita Diamonds) and then (briefly) a combination Dojo + Co-Working space, and now is a coffee shop. Shortly after I started working @ HP and learning the joy of X Windows, I had a need for volume 0, 1, 2, 3, 4, and Motif. The books I bought were in the transition period from X11R4 to X11R5, so the previous edition to the pink one, and the same as the blue one.
People in the comments stream were laughing about 30 year old books. And I was like, 30 years old? They can't be, I just bought those in 1991. OK, turns out that is only 28 years ago. Sigh. I remember them being ludicrously expensive, I could only afford one every second month.
In those days knowledge was harder to come by. There was no www, no search engine. You walked downtown, into a multi-story book store, and wandered around, discovering things you never knew existed, and taking them home.
Interestingly my desktops all still run X Windows, a testament to its staying power. There's more pixels, and more colours, but its essentially the same.